PLANT DISEASES 



317 



PEA 



Leaf spots (Ascochyta Pisi). Small, 

 circular spots with dark borders and lighter 

 centers, bearing small, black pimple-like 

 bodies, form on the leaves. Similar spots 

 are found upon the pods and stems, ^ which 

 also, are attacked. Avoid use of diseased 

 seed. 



PEACH 



Brown rot (See Cherry). Dust with 

 sulfur and arsenate of lead. Use a 90-10 

 mixture. 



Leaf curl (Exoascus deformans). At 

 first the new leaves swell and wrinkle, the 

 leaf -blade puckering along the midrib. 

 At this time the leaf is peculiarly colored 

 with red and yellow tints. Later the upper 

 portions of the affected leaf turn whitish 

 and assume a velvety appearance. Spray 

 in the Fall or the early Spring before the 

 buds swell, with lime-sulfur (1-15). Cover 

 every bud. 



Yellows (Cause unknown). May be 

 recognized by the yellowish color of the 

 foliage and the premature development of 

 the fruit. The appearance of an excessive 

 number of slender yellowish shoots occurs 

 in advanced stages of the disease. Destroy 

 affected trees. Do not drag them through 

 the orchard. 



Scab (Cladosporium Carpophilum). Oli- 

 vaceous to black, scabby patches on the 

 fruit and twigs. When severe the spots run 

 together. The fruit is often distorted and 

 the skin may crack open. Spray with self 

 boiled lime-sulfur (8-8-50) four to five weeks 

 after the petals fall, and again three weeks 

 later, or better, dust with sulfur and arse- 

 nate of lead, as for brown rot. 



PEAR 



Fire blight (Bacillus amylovorus) . The 

 blossoms, young fruit and twigs appear as if 

 burned, but affected leaves remain attached 

 to the twigs. Cankers are formed on the 

 larger limbs and in the Spring milky drops 

 filled with bacteria exude from them. Cut 

 out the cankers in the fall and early spring 

 and disinfect the wound with corrosive 

 sublimate _ (1-1000). Later paint over 

 wounds with coal tar. During the Summer 

 remove diseased spurs and twigs as fast as 

 they appear and disinfect cut surfaces with 

 corrosive sublimate. 



Leaf spot (Mycosph/ierella sentina) . 

 Small angular spots with definite dark 

 colored margins and grayish white centers 

 are found on the leaves. Spray with lime- 

 sulfur (1-50) just after the petals fall, 

 two weeks later, and again in another two 

 weeks. 



Scab {Venturia Pyrina) . See Apple scab . 



PEONY 



Blight (Botrytis Paeoniae). Causeb a 

 rotting off of young shoots early in Spring. 

 Brownish spots with target board markings 



form on the leaves. In moist weather a 

 grayish fuzz may be observed upon these 

 diseased portions. The same disease blasts 

 the buds.' Sometimes small black bodies 

 are produced on the rotted stems. Remove 

 and burn the diseased parts. Spray with 

 Bordeaux mixture. 



PLUM 



Black knot {Plowrightia morbosa). Knots 

 from }/2 in. to several inches in length are 

 produced on the young twigs. At first 

 olivaceous in color, they later turn to a coal 

 black. Frequently the twigs on which knots 

 form are bent back upon themselves. Re- 

 move and burn the knots in the Fall or 

 early Winter. 



Brown rot. See Cherry. 



Shot hole (Coccomyces prumophorae) . 

 See Cherry. 



POTATO 



Blight (Phytophthora infestans). Spots, 

 black in the center and with a water-soaked 

 margin, begin to develop, usually at the tip 

 or margin of the leaves. Under moist con- 

 ditions a white frost-like down encircles the 

 diseased portion. Soon the whole plant 

 dies. At this time an offensive odor is 

 developed. Spray with Bordeaux mixture 

 (5-5-50) when the plants are about 6 in. 

 high. Follow with other sprayings about 

 10 days apart. Spray just ahead of rain 

 periods if possible. 



Rhizoctonia stem rot (Corticium 

 vagum). Small, brownish black bodies 

 which may be easily removed from the 

 skin, form on the surface of the tubers. The 

 sprouts often rot before they get through 

 the ground. The stem near the ground is 

 also attacked and often rotted. Plants 

 grown from such seed produce many little 

 potatoes. Treat the seed with corrosive 

 sublimate (4 ounces to 30 gallons) for 

 IJ^ hours. 



Scab {Actinomyces scabies). Rough scabs 

 on the surfaces of the potato. Usually the 

 margin is raised and the center depressed. 

 Avoid the addition of lime or wood ashes 

 to the soil. Treat seed with corrosive sub- 

 limate solution, (4 ounces to 30 gallons of 

 water), for 13^ hours. 



RASPBERRY 



Anthracnose {Plectodiscella veneta). 

 Affects principally the canes, which at first 

 show small, purplish elliptical spots. Later 

 these become larger and somewhat sunken 

 and the centers turn a grayish white. 

 Sometimes these spots run together and 

 large areas of the stems become diseased. 

 Remove diseased canes. Set only plants 

 free from the disease. Spray with Bor- 

 deaux mixture (4-4-50). 



Orange rust (Gymnoconia interstitialis) . 

 A bright orange colored rust covering the 

 under side of the leaves which become dwarf- 

 ed and rolled . Dig up and destroy diseased 

 plants. 



